<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>hello</title>
    <style>
        fieldset
        {
            width: 400px;
        }
    </style>
</head>
<body>
    <h1>hello world</h1>
    <form action="post">
        <fieldset>
            <legend>输入账号密码登录</legend>
            <span>
                username: <input type="text" name="username">
            </span>
            <br>
            <span>
                password: <input type="password" name="password">
            </span>
            <br>
            <span>
                <input type="button" value="提交">
            </span>
        </fieldset>
    </form>
</body>
</html>